Fifty years ago today, the United States entered an unfamiliar territory known as the nuclear test moratorium.

President Dwight Eisenhower halted all nuclear testing for one year, beginning Oct. 31, 1958. It was the first significant step back from an arms race that had taken on a new dimension in the era of the hydrogen bomb, a thousand times more powerful than the weapon used on Hiroshima at the end of World War II.

The moratorium, with extensions and a frightening intermission that included the Cuban Missile Crisis, led to the end of atmospheric testing in the world.

Dave Thompson, a retired physicist from Los Alamos National Laboratory and author of “A Guide to the Nuclear Arms Control Treaties,” said Thursday that he recalled the moratorium very well and how it affected the laboratory at the time.

“The people I was around were very much in favor of verifiable arms control,” he said. “That was my own feeling.”

Thomson said he had finished his thesis in 1960 at the laboratory and was looking for another job during the moratorium. In fact there were a number of opportunities available in the test division.

“There was a wait and see mode, trying to retain capabilities if you had to return to testing in Nevada,” he said. “And there were at least three test groups in that division that were capable of long term programs.”

The Union of Soviet Socialist Republics, as the great nuclear rival was known in those days, had unilaterally announced its moratorium seven months earlier.

France would interrupt the process by beginning its first nuclear tests in late 1960. The U.S., U.S.S.R. and British governments also strayed emphatically from the path from the end of 1961 until the signing of the first real deal, the Limited Test Ban Treaty of 1963.

The period figures prominently in histories of arms control and has been extensively documented by the National Security Archives (NSA) at George Washington University.

Scholars like Lawrence S. Wittner, a professor of history at the State University of New York, have made use of those and other documents to draw out the historical significance of the pause.

Writing earlier this year for the History News Network, Wittner suggested that the Cold War moratorium half a century ago should hearten contemporary peace advocates, who might feel disillusioned by the futility of their war protests.

It may be too early to say, he wrote, offering the test moratorium as an example of the power of longterm protest.

“By 1958, worldwide concern for radioactive fallout had reached major proportions, including major demonstrations,” Thomson noted in his book.

Documents in the archives illustrate pressures from world public opinion concerning global fallout and from U.S. allies, along with concerns over the status of the Soviet nuclear weapons program and the proliferation of nuclear capabilities.

A State Department memo from August 1958 records a discussion in which “Edward Teller, the director of Livermore Radiation Laboratory, a major opponent of the ban, argued that it would be possible to ‘dampen’ the seismic signals produced by underground tests while Carson Mark, of Los Alamos Laboratory, took a contrary view.”

The moratorium was threatened after the American U-2 reconnaissance plane was shot down over Soviet territory on May 1, 1960, aggravating fundamental disagreements on verification.

Thomson said the U-2 flights were needed because the U.S. hadn’t developed its satellite capabilities yet.

“Just before the Paris summit, Eisenhower ordered a U-2 flight for one last look,” Thompson said.

Then, according to the NSA briefing paper, the Soviets broke the moratorium on September 1961 during the heightened tensions over the status of West Berlin and the construction of the Berlin Wall.

Kennedy resumed underground testing shortly afterward, but he delayed atmospheric testing until the following spring. Both sides pulled out the stops after that and conducted more than 200 weapons tests during 1961 and 1962.

“The moratrorium laid the groundwork for the Limited Test Ban Treaty of 1963,” said Thomson. “It was the first major milestone in arms control.”

Banning nuclear tests in the atmosphere, outer space or under water, the moratorium did not yet include measures for on-site inspections.

During Senate hearings over ratification, Thomson wrote, there was strong opposition led by Sen. Barry Goldwater, but the testimony by Norris Bradbury, the director of the Los Alamos Scientific Laboratory at the time, was persuasive in assuring the Senate that “American security would not be at a disadvantage relative to the Soviets.”

All nuclear testing, including the underground tests that continued after 1963, finally ceased in 1992, also as a moratorium that continues to be extended and affirmed. Although the Comprehensive Test Ban Treaty was successfully negotiated in 1996, it has yet to be ratified by the Senate.